Try to heat up the nozzle so evey filament in the machine get melted, then remove nozzle clean eat, look if there is any parts that needs to be cleaned or may be a object that jam your material, if so adjust it correctly.

It kind of depends, if you really wants sales, I think you should put your design on both sites: That said, Thingiverse and youmagine. But you can always set a cheaper price for youmagine if you wanna support Ultimaker. Smart plan huh?